The objectives of the proposed work are: 1) To investigate the biological functions of HMG-1 and HMG-2, two nonhistone chromatin proteins that occur in much higher amounts in a line of hepatoma tissue culture cells (HTC cells) than in adult rat liver and that are in that sense tumor-enriched species. Much of the proposed work will deal with possible functional implications of the proteins' preferential affinity for single-stranded DNA. We will, in particular, attempt to determine if the proteins are required for DNA replication or for transcription, two major nuclear processes in which single-stranded DNA is transiently required. 2) To identify other nonhistone chromatin proteins that are enriched in rapidly divding cells. 3) To isolate individual nonhistone chromatin proteins, other than HMG-1 and HMG-2, that are enriched in prolierating cells to allow detailed investigation of the proteins in an attempt to eludicate their functions. The proposed work, then, is a study of the biochemistry and molecular biology of nuclear proteins that might be involved in cell proliferation. As such it should contribute to an eventual understanding of proliferative disorders, such as cancer.